Researchers find bottom of Pacific getting colder, possibly due to Little Ice Age

Earth's climate cooled considerably across the transition from the Medieval Warm Period to the Little Ice Age about 700 years ago. Theoretically, owing to how the ocean circulates, this cooling should be recorded in Pacific deep-ocean temperatures, where water that was on the surface then is found today. Gebbie and Huybers used an ocean circulation model and observations from both the end of the 19th century and the end of the 20th century to detect and quantify this trend. The ongoing deep Pacific is cooling, which revises Earth's overall heat budget since 1750 downward by 35%.

The model showed that the Pacific Ocean cooled over the course of the 20th century at depths of 1.8 to 2.6 kilometers. The amount is still not precise, but the researchers suggest it is most likely between 0.02 and 0.08° C. That cooling, the researchers suggest, is likely due to the Little Ice Age, which ran from approximately 1300 until approximately 1870. Prior to that, there was a time known as the Medieval Warm Period, which had caused the deep waters of the Pacific to warm just prior to the cooling it is now experiencing.

Pacific Depths Likely to Keep Warming for Centuries Even if We Decarbonize Now, Study Shows

The slow-circulating deep Pacific is still cooling almost 200 years after the Little Ice Age ended, with worrying implications for the anthropogenic age

There is also no question that anthropogenic climate change is warming ocean surfaces and even the groundwater.

Because of how water circulates in the vast oceans, the oceanographers had suspected that temperature anomalies like the Little Ice Age might leave long-term traces in the overturning deep Pacific. The still-cooling water they have observed is just such a “memory,” they believe.

Their paper presents a model of the behavior of the “creeping waters,” not categorical facts. But they’re confident in it and if they’re right, one implication of their model is that even if we suddenly decarbonize and stop changing the climate, we could be contending with the depths of the Pacific Ocean continuing to warm at least for decades, possibly hundreds of years.

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In the meantime, scientists are working to understand why the magnetic field is changing so dramatically. Geomagnetic pulses, like the one that happened in 2016, might be traced back to ‘hydromagnetic’ waves arising from deep in the core1. And the fast motion of the north magnetic pole could be linked to a high-speed jet of liquid iron beneath Canada2.

The jet seems to be smearing out and weakening the magnetic field beneath Canada, Phil Livermore, a geomagnetist at the University of Leeds, UK, said at the American Geophysical Union meeting. And that means that Canada is essentially losing a magnetic tug-of-war with Siberia.

“The location of the north magnetic pole appears to be governed by two large-scale patches of magnetic field, one beneath Canada and one beneath Siberia,” Livermore says. “The Siberian patch is winning the competition.”

Which means that the world’s geomagnetists will have a lot to keep them busy for the foreseeable future.

If geologic history repeats itself, Earth’s magnetic poles should eventually swap places. This much is undeniable. Based on the magnetic fingerprints locked into ancient rocks, we know that over the last 20 million years, magnetic north and south have flipped roughly every 200,000 to 300,000 years (this rate has not been constant over the planet’s lifetime, though). The last of these major reversals occurred about 780,000 years ago, although the Poles do wander around in between these larger flips. (What’s more, climate change seems to be shifting Earth’s geographic poles.)

That means we’re a bit overdue for a total reversal, and some data do, in fact, suggest that a geomagnetic reversal is geologically imminent. But this does not mean a polar flip-flop is going to happen tomorrow, or even any time soon, and we’d put good money on North still being in the Arctic for a while—although neither we nor anyone else knows when the next total reversal will actually happen.

Close encounters with ∞Infinity∞"So much joy I cry, so much pain I laugh."The ink of the scholar is more sacred than the blood of the martyr.Remember, you need more than one note to make beautiful music.Love is the missing link!